1. Field of the Invention
The present invention relates to an image forming apparatus.
2. Discussion of the Related Art
The photoreceptor (i.e. photoconductor) unit for use in an image forming apparatus such as a facsimile device, a copying machine or a printer which forms an image by the electrophotographic process is categorized into a drum-shaped photoreceptor formed of a metal tube covered with a photoreceptor layer formed by vapor deposition or coating process, a so-called take-up type photoreceptor constructed such that a sheet-like photoreceptor is removably wound around a tubular support, a so-called clamp type photoreceptor constructed such that an endless photoreceptor is supported on the circumferential outer surface of a tubular support by means of a clamp mechanism provided in association with the tubular support, a belt-type photoreceptor constructed such that a photoreceptor shaped like an endless belt is internally supported by at least two rolls, and others. The photoreceptor materials currently used for the photoreceptor unit are Selenium (Se), organic photoconductive material (OPC), amorphous silicon (a-Si), zinc oxide, and the like.
In grouping plural types of image forming apparatus into different model series on the basis of printing speed, the systems of each different type of the apparatus are used. Accordingly, the cost of production is inevitably increased.